Electrical heater for tubular



Jan. 1, 1935. E. F, HoLlNGER ELECTRICAL HEATERv FOR TUBULAR BOILERS AND LIKE APPARATUS original Filed July 25, 1928 xNvENToR Emil F. HoLNGER.

ATTORNEY' L Il il...

, m mmf Patented Jan. l., 1935 UNITED STATES `PATENT OFFICE ELECTRICAL HEATER FOR TUBULAR BOILERS AND LIKE APPARATUS Emil F. Holinger, New York, N. Y., assigner to Hudson Electrical Heating Corporation, New York, N. Y.. a corporation of New York 12 Claims.

5 July 25, 1928.

The invention is specially designed to produce a form of electrical heating apparatus which can be safely inserted in 'the tubes of fire tube boilers and operate efficiently therein. To this end the heater unit extends from either end of the boiler tube and is supported at a distance therefrom in the preferred form and the heating coil or electric resistor is kcontained in a perforated cylinder which permits air to circulate through it, but prevents the resistor from coming in contact with the boiler tube in case it sags or breaks. The best form of apparatus at present known to me embodying my invention is illustrated in the accompanying figure of drawing which is an axial section of a boiler tube and heating unit therein, the parts being broken away.

1 represents the tube of a tubular boiler or heater mounted in the boiler heads 2, 2, with its outer ends expanded to make water tight joints therewith in the usual way. 3, 3, are the customary casing heads for the boiler, usually comprising non-heat-conducting material. 4 is the outer tube or casing of the heating unit, which has a series of spaced apart perforations '14, 14, in its wall. This tube 4 is usually rmade of metal, and is held in position by the exterior nuts 5, 5, threaded onto its ends which project beyond the casing heads 3, 3.

6 is a coil of resistant, electrically conductive material such as a nichrome steel which preferably is slightly malleable rso that portions of it can be bent into any desired form.

7, 7, are threaded bolts mounted in spools of refractory insulating material 11, 11, which fit snugly into the ends of heater tube 4. Preferably each of these bolts has an .outwardly aring head 8, and a nut 9 threaded on it adjacent said head, said nuts being each provided with an outwardly flaring recess 10, having the same angle of ilare as the bolt head 8. These bolts and their supporting refractories are so placed in the tube 4 that the bolt heads 8 are inside of the tube, while the other ends `of the bolts which carry the spherical nuts 1-9, 19, are outside of the tube. The bolts 7 are clamped in the spools 11, by means of exterior nuts 17, cooperating with the interior nuts 9.

The ends 6a of the heating coil 6 are clamped between bolt heads and nuts9, as shown at the left hand portion of the drawing, and the coil is supported at intermediate points by buttons lla of refractory insulating material which are similar to spools 1l, ll, except that they may be made shorter. All of these buttons have projecting flanges 13, 13, at either end preferably of outwardly tapering cross section, as shown, and are also provided with transverse exterior grooves or keyways 15, 15. Some form of keying means are employed to hold spools 11 and buttons 11a, in place in tube 4. Thus 16, 16, represent keys which may be formed of somewhat flexible wire of a length sufficient to allow them tofrest in keyways l5, 15, with their ends projecting into certain of the holes 14 in tube 4. Bodies of cement are then pressed in through holes 14, after keys 16 have been placed in position, to lll the holes 14, and occupy portions of grooves 15, 15, around keys 16, 16. When this cement sets, the keys are obviously locked in position, and each of the spools 11 and buttons 11a. .thereby held against any sliding movement in tube 4.

The advantages of the construction above described comprise the efficient support of the heating coil, its eiective insulation from the tube 4 by Ithe spools 11 and buttons 11a in that they provide an inner insulating surface which is protected from the deposition of moisture or other conducting material, and the solidity of the refractory units employed, which latter will hold the heating coil securely without being liable to fracture themselves, either by unequal expansion vor contraction of the parts or by the impacts resulting from a rigid electric locomotive usually supported by Nery stiff springs, pounding and jolting over frogs, switches and rail joints in its operation. If the tube 4 expands more rapidly than the spools 11, and buttons 11a, under the application of heat, the radially projecting ends of the keys 16 will merely slip back and forth in the holes 14, without materially fracturing the surrounding body of cement and without any possibility of the keys being displaced so they can fall out. Even if some of said keys are sufficiently displaced to comefin contact with boiler tube 1, no short circuit is produced because the heating coil and its connections are still completely insulated from tube 4 by spools 11, and buttons 11a.

A special advantage in operation results from the free circulation of air through the casing head compartment, boiler tube 1, openings 14, and interiors of tubes 4, and in intimate contact with heating coils 6. Such free circulation ing a second set of tubes each of which extends through a boiler tube, but is not in contact therewith, and contains an electrical resistance element suitably insulated therefrom, the combination, with said above described structure, of means constituting the sole supports for said second set of tubes located exteriorly of, and spaced away from, the water tubes and tube sheets of said boiler; whereby a free circulation of air through said water tubes and around said second set of tubes and around the resistance elements therein may be created when said resistance elements are heated by the passage of current through them.

2; The combination such as defined in claim l in which said second tube has perforations in its walls through which the said air current may also circulate.

3. A structure such as dened in claim 1 in which said second tube is made of metal with perforations in its walls, combined with insulat-Y ing supports for maintaining said resistance element in said second tube out of Contact with the' walls thereof.v

4. An electric heating structure having in combination a plurality Vof heating units each comprising a casing forming an interior heat transmission chamber for containing a uid medium to be heated therein and having a resistance element located therein, a perforate wall rstructure for said interior heat transmission chamber, together with an exterior casing forming aheat transmission chamber circumferentially surrounding a considerable portion of said interior casing, and to which a iiuid medium to be heated may be admitted, which structure as a whole has means for heat transmission within it from each of said units to the others and is also provided with means to prevent escape from said entire heating structure of any medium heated therein.

5. An electric heating structure having in combination a plurality of units each comprising a resistance element, a casing forming an interior heat transmission chamber for containing the fluid medium to be heated therein, a perforate wall structure for said interior heat transmission chamber and an exterior casing forming a heat transmission chamber circumferentially surrounding a considerable portion of said interior casing and to which a fluid medium to be heated may be admitted, together with means located exteriorly of said exterior casing to support the `interior casing; which said structure as a whole has means for heat transmission within it from each of said units to the others and also is provided with means to prevent escape from said ventire heating structure of any medium heated therein.

6. An electric heating structure for boiler tubes comprising a perforated tube extending through a boiler tube, means supporting said perforated tube in heads external to the boiler tube in spaced relation to the interior wall of the boiler tube, a refractory spool vdisposed in each end of said perforated tube, a screw threaded bolt extending through each of said spools with the head of each of said bolts disposed interior of said perforated tube and with the screw threaded end of the bolts extending beyond the heads of the boiler and forming electric terminals, and a resistance element disposed between the heads of said bolts centrally of said perforated tube.

'7.` An electric heating structure for boiler tubes comprising a perforated tube extending through a boiler tube, means supporting said perforatedfgtube in heads external to the boiler tube inV spaced relation to the interior wall of the boiler tube, a refractory spool disposed in each end of said perforated tube, a screw threaded bolt extending through each of said spools with the head of each of said bolts disposed interior of said perforated tube and with the screw threaded end of the bolts extending beyond the heads of the boiler and forming electric terminals, a resistance element disposed between the heads of said bolts centrally of said perforated tube, and insulator members disposed at spaced intervalsA in said perforated tube for maintaining said resistance element in spaced relation to the interior walls of said perforated tube.

8. lAn electric vheatingstructure for boiler tubes comprising a tubular member extending through a boiler tube in spaced relation to the interior wall of the boiler tube, a supporting connection between the ends of said tubular member and the boiler heads, said tubular member having perforate sections and imperforate sections, a refractory spool closing each end of said tubular member, a screw threaded member extending through eachv of said refractory spools and having an electric terminal on the ends external 4of the boiler heads and heads on the ends interior of said tubular member, and an electric resistor supported between the heads on said screw threaded members.

9. An electric heating structure for boiler tubes comprising a tubular member extending through a boiler tube in spaced relation to the interior wall ofthe boiler tube, a supporting connection between the ends of said tubular member and the boiler heads, said tubular member having perforate sections and imperforate sections, a refractory spool closing each end of said tubular member, a screw threaded member extending through each of said refractory spools and having an electric terminal on the ends external of the boiler heads and heads on the ends interior of said tubular member, an electric resistor supported between the heads on said screw threaded members, and means intermediate the perforate sections of said tubular member for insulatingly maintaining said resistor centrally of said tubular member.

10. An electric heating structure for boiler tubes comprising a tubular member extending through a boiler tube in spaced relation to the interior wall of the boiler tube, a supporting connection between the ends of said tubular member and the boiler heads, said tubular member having perforate sections and imperforate sections, a refractory spool closing each end of said tubular member, a screw threaded member extending through each of said refractory spools and having an electric terminal on the ends external of the boiler heads and heads on the ends interior of said tubular member, and an electric resistor and screw threaded devices engaging the ends of said screw threaded members and coacting with the heads thereon for gripping and maintaining V.said resistor axially of said tubular member in spaced relation to the interior wall thereof.

11. An electric heating structure for boiler tubes comprising a tubular member extending through a boiler tube in spaced relation to the interior wall of the boiler tube, a supporting connection between the ends of said tubular member and the boiler heads, said tubular member having perforate sections and imperforate sections, a refractory spool closing each end of said tubular member, aI screw threaded member extending through each of said refractory spools and having an electric terminal on the ends external of the boiler heads and frusto conical heads on the ends interior of said tubular member, an electrical resistor element, screw threaded devices engaging said screw threaded members and coacting with said frusto conical heads for supporting said electrical resistor element centrally of said tubular member.

12. An electric heating structure for boiler tubes comprising a tubular member extending through a boiler tube in spaced relation to the interior wall of the boiler tube, a supporting connection between the ends of said tubular member and the boiler heads, said tubular member having perforate sections and imperforate sections, a refractory spool closing each end of said tubular member, a screw threaded member extending through each of said refractory spools and having an electric terminal on the ends external of the boiler heads and frusto conical heads on the ends interior of said tubular member, an electrical resistor element, screw threaded devices engaging said screw threaded members and coacting with said frusto conical heads for supporting said electrical resistor element, and insulators spaced at intervals in said tubular member and supporting said resistor element in spaced relation to the interior wall of said tubular member.

EMIL F. HOLINGER. 

